Delivery systems

ABSTRACT

A delivery system comprising a covering having at least two compartments is provided. A first compartment contains a first therapeutic agent and the second compartment can be unfilled and is configured to receive a second therapeutic agent. The first compartment and the second compartment are separated by at least one removable separation member, for example a drawstring, that can be pulled to allow the first and second therapeutic agents to mix prior to delivery at a selected surgical site. Either the first or second compartment of the covering define an opening further comprising a pre-attached sealing member, which can be a flap sealable by heat, sutures, pressing or interference fittings. The opening of the empty compartment can be configured to receive a filling member, such as a funnel fitted with a spring loaded clip for temporary attachment to the covering. A method of treating a bone defect in a patient utilizing the delivery system is also provided.

FIELD

A delivery system for delivering therapeutic agents to a surgical site is provided. More particularly, the delivery system includes a covering having separate compartments for combining demineralized bone particles with grafting materials, the covering configured for containing and mixing the therapeutic agents prior to delivery at a surgical site.

BACKGROUND

The use of bone grafts and bone substitute materials in orthopedic medicine is known. While bone wounds can regenerate without the formation of scar tissue, fractures and other orthopedic injuries take a long time to heal, during which time the bone is unable to support physiologic loading unaided. Metal pins, screws, rods, plates and meshes are frequently required to replace the mechanical functions of injured bone. However, metal is significantly more stiff than bone. Use of metal implants may result in decreased bone density around the implant site due to stress shielding. Physiologic stresses and corrosion may cause metal implants to fracture. Unlike bone, which can heal small damage cracks through remodeling to prevent more extensive damage and failure, damaged metal implants can only be replaced or removed. The natural cellular healing and remodeling mechanisms of the body coordinate removal of bone and bone grafts by osteoclast cells and formation of bone by osteoblast cells.

Conventionally, bone tissue regeneration is achieved by filling a bone repair site with a bone graft. Over time, the bone graft is incorporated by the host and new bone remodels the bone graft. In order to place the bone graft, it is common to use a monolithic bone graft or to form an osteoimplant comprising particulated bone in a carrier. The carrier is thus chosen to be biocompatible, to be resorbable, and to have release characteristics such that the bone graft is accessible.

The rapid and effective repair of bone defects caused by injury, disease, wounds, or surgery is a goal of orthopedic surgery. Toward this end, a number of compositions and materials have been used or proposed for use in the repair of bone defects. The biological, physical, and mechanical properties of the compositions and materials are among the major factors influencing their suitability and performance in various orthopedic applications.

Demineralized bone matrix (DBM) implants have been reported to be particularly useful. Demineralized bone matrix is typically derived from cadavers. The bone is removed aseptically and/or treated to kill any infectious agents. The bone is then particulated by milling or grinding and then the mineral components are extracted for example, by soaking the bone in an acidic solution.

Some DBM formulations have various drawbacks. For example, while the collagen-based matrix of DBM is relatively stable, the active factors within the DBM matrix are rapidly degraded. The osteogenic activity of the DBM may be significantly degraded within 24 hours after implantation, and in some instances the osteogenic activity may be inactivated within 6 hours. Therefore, the factors associated with the DBM are only available to recruit cells to the site of injury for a short time after transplantation. For much of the healing process, which may take weeks to months, the implanted material may provide little or no assistance in recruiting cells.

Attempts to overcome these problems have lead researchers to utilize delivery systems such as polymer mesh bags to release DBM at a surgical site. However, any additional bone graft material, such as for example, autologous bone or growth factors, would have to be placed underneath or on top of the DBM mesh bag which approach is, typically, not recommended for inducing new bone formation.

Thus, there is a need to improve the efficacy and consistency of DBM delivery systems by mixing the DBM particles/fibers with other bone graft materials such as autologous bone and other therapeutic agents throughout the mesh bag prior to, during or after the surgical procedure. It would therefore be desirable to provide delivery systems that are configured to allow live cells and other therapeutic agents to be in close contact with DBM particles/fibers so as to induce bone growth throughout the graft material rather than primarily along the surface of the DBM containing delivery system.

SUMMARY

Accordingly, a delivery system for delivering DBM mixed with one or more therapeutic agents is provided. Generally, the delivery system comprises a covering having at least two compartments, a first compartment containing a first therapeutic agent and a second compartment configured to receive a second therapeutic agent. The first compartment and the second compartment are separated by at least one removable temporary separation member, for example a drawstring that can be pulled to allow the first and second therapeutic agents to mix prior to delivery at a selected surgical site.

Either the first or the second compartment can be provided unfilled. Either the first or second compartment of the covering define an opening further comprising a pre-attached sealing member. In several embodiments, the sealing member can be a flap sealable by heat, sutures, pressing or interference fittings. The opening of the empty compartment can be configured to receive a filling member for filling the empty compartment with a therapeutic agent such as autograft material. In various embodiments, the filling member can be a funnel, a spoon, a syringe or any device that can function to fill the empty compartment with a therapeutic agent. The delivery system provided in this disclosure further comprises an attachment element cooperatively attached to the filling member or the covering in order to maintain the empty or second compartment open for filling with a second therapeutic agent. In some aspects, the attachment element can be a spring loaded clip, a friction or an interference fitting.

In various embodiments, the first therapeutic agent placed in the first compartment comprises demineralized bone matrix and the second therapeutic agent placed in the second compartment comprises a protein (e.g., bone morphogenetic protein) carbohydrate, lipids, collagen, allograft bone, autograft bone, tricalcium phosphate, hydroxyapatite, growth and differentiation factors, carriers for growth factors, growth factors extracts of tissue, bone marrow aspirate, concentrates of lipid derived or marrow derived adult stem cells, umbilical cord derived stem cells, committed or partially committed cells from osteogenic or chondrogenic lineage, antimicrobials, antibiotics, statins, or combinations thereof.

In other embodiments, the present disclosure provides a delivery system including a covering configured for implantation into a bone defect site. The covering can have at least two compartments, a first compartment containing a first therapeutic agent, for example DBM and a second unfilled compartment configured to receive a second therapeutic agent, wherein the covering retains the first therapeutic agent for mixing with the second therapeutic agent prior to delivery at a surgical site. The at least two compartments of the covering can be separated by at least one removable temporary separation member, the second compartment defining an opening further comprising a pre-attached sealing member. The pre-attached sealing member comprises a flap sealable by sutures, heat or any other sealing means. The delivery system can be a porous mesh and includes an attachable filling member configured to fit over the opening of the second empty compartment for filling with a therapeutic agent such as autograft. The filling member also includes an attachment member that can be, in some aspects, a spring loaded clip, a friction or interference fitting. The temporary separation member can be removed to allow for the first and second therapeutic agents to mix thoroughly prior to delivery at a surgical site.

In various embodiments, a method of treating a bone defect in a patient in need of such treatment is provided. The method described in this disclosure comprises implanting into the bone defect a delivery system comprising a covering having at least two compartments, a first compartment containing a first therapeutic agent and a second compartment configured to receive a second therapeutic agent, wherein the covering retains the first therapeutic agent for mixing with the second therapeutic agent prior to delivery at a surgical site, the at least two compartments being separated by at least one removable separation member, the second compartment defining an opening further comprising a pre-attached sealing member.

In other aspects, the method of treating the bone defect further comprises the step of mixing of the first and second therapeutic agents by removing the removable separation member, for example a drawstring. In certain embodiments, the method of treating the bone defect can further include the step of shrinking or reducing in size the delivery system by removing the removable separation member. In various aspects, the method of treating a bone defect further includes attaching a filling member, for example a funnel, to the unfilled compartment, the filling member including an attachment member such as a spring loaded clip, a friction or interference fitting.

In some embodiments, the elongated containment portion of the covering has a cross sectional shape selected from generally circular or generally oval and a shape that can be tubular, rectangular, or cubic. The covering can have two ends opposite each other and sides connected to the two ends defining a cylinder, rectangle, tube or other volumetric forms. The covering can be made from porous mesh to provide, for example, a porous mesh bag.

In some embodiments, some of the compartments are unfilled at manufacture but are configured to be filled prior to or during the surgical procedure.

Additional features and advantages of various embodiments will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practice of various embodiments. The objectives and other advantages of various embodiments will be realized and attained by means of the elements and combinations particularly pointed out in the description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In part, other aspects, features, benefits and advantages of the embodiments will be apparent with regard to the following description, appended claims and accompanying drawings where:

FIG. 1 illustrates a side view of a delivery system comprising a covering having three compartments in accordance with one embodiment of the present disclosure;

FIG. 2 illustrates a top view of a delivery system comprising a covering also having three compartments in accordance with another embodiment of the present disclosure;

FIG. 3 illustrates a side view of a delivery system including a covering having two compartments in accordance with another embodiment of the present disclosure; and

FIG. 4 illustrates a side view of a filling member in accordance with an embodiment of the present disclosure.

It is to be understood that the figures are not drawn to scale. Further, the relation between objects in a figure may not be to scale, and may in fact have a reverse relationship as to size. The figures are intended to bring understanding and clarity to the structure of each object shown, and thus, some features may be exaggerated in order to illustrate a specific feature of a structure.

DETAILED DESCRIPTION Definitions

It is noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the,” include plural referents unless expressly and unequivocally limited to one referent. For example, reference to “a compartment” includes one, two, three or more compartments.

“Therapeutic agent or bioactive compound,” as used herein, refers to a compound or entity that alters, inhibits, activates, or otherwise affects biological or chemical events. For example, bioactive agents may include, but are not limited to, osteogenic or chondrogenic proteins or peptides, anti-AIDS therapeutic agents, anti-cancer therapeutic agents, antibiotics, immunosuppressants, anti-viral therapeutic agents, enzyme inhibitors, hormones, neurotoxins, opioids, hypnotics, anti-histamines, lubricants, tranquilizers, anti-convulsants, muscle relaxants and anti-Parkinson therapeutic agents, anti-spasmodics and muscle contractants including channel blockers, miotics and anti-cholinergics, anti-glaucoma compounds, anti-parasite and/or anti-protozoal compounds, modulators of cell-extracellular matrix interactions including cell growth inhibitors and antiadhesion molecules, vasodilating agents, inhibitors of DNA, RNA or protein synthesis, anti-hypertensives, analgesics, anti-pyretics, steroidal and non-steroidal anti-inflammatory agents, anti-angiogenic factors, angiogenic factors, anti-secretory factors, anticoagulants and/or antithrombotic agents, local anesthetics, ophthalmics, prostaglandins, anti-depressants, anti-psychotic therapeutic agents, anti-emetics, and imaging agents. In certain embodiments, the bioactive agent is a drug. The therapeutic agent, in some embodiments, can include bone, bone cells, other cells, bone substitutes, DBM, or the like. In some embodiments, the bioactive agent or therapeutic agent is a growth factor, cytokine, extracellular matrix molecule or a fragment or derivative thereof, for example, a cell attachment sequence such as RGD.

“Biocompatible,” as used herein, refers to materials that, upon administration in vivo, do not induce undesirable long-term effects.

“Bone,” as used herein, refers to bone that is cortical, cancellous or cortico-cancellous of autogenous, allogenic, xenogenic, or transgenic origin.

“Demineralized,” as used herein, refers to any material generated by removing mineral material from tissue, for example, bone tissue. In certain embodiments, the demineralized compositions described herein include preparations containing less than 5% calcium and preferably less than 1% calcium by weight. Partially demineralized bone (e.g., preparations with greater than 5% calcium by weight but containing less than 100% of the original starting amount of calcium) is also considered within the scope of the invention. In some embodiments, demineralized bone has less than 95% of its original mineral content. Demineralized is intended to encompass such expressions as “substantially demineralized,” “partially demineralized,” and “fully demineralized.”

“Demineralized bone matrix,” as used herein, refers to any material generated by removing mineral material from bone tissue. In preferred embodiments, the DBM compositions as used herein include preparations containing less than 5% calcium and preferably less than 1% calcium by weight. Partially demineralized bone (for example, preparations with greater than 5% calcium by weight but containing less than 100% of the original starting amount of calcium) are also considered within the scope of the invention.

“Osteoconductive,” as used herein, refers to the ability of a non-osteoinductive therapeutic agent to serve as a suitable template or therapeutic agent along which bone may grow.

“Osteogenic,” as used herein, refers to the ability of an agent, material, or implant to enhance or accelerate the growth of new bone tissue by one or more mechanisms such as osteogenesis, osteoconduction, and/or osteoinduction.

“Osteoimplant,” as used herein, refers to any bone-derived implant prepared in accordance with the embodiments of this invention and therefore is intended to include expressions such as bone membrane, bone graft.

“Osteoinductive,” as used herein, refers to the quality of being able to recruit cells from the host that have the potential to stimulate new bone formation. Any material that can induce the formation of ectopic bone in the soft tissue of an animal is considered osteoinductive. For example, most osteoinductive materials induce bone formation in athymic rats when assayed according to the method of Edwards et al., “Osteoinduction of Human Demineralized Bone: Characterization in a Rat Model,” Clinical Orthopaedics & Rel. Res., 357:219-228, December 1998, incorporated herein by reference.

“Superficially demineralized,” as used herein, refers to bone-derived elements possessing at least about 90 weight percent of their original inorganic mineral content, the expression “partially demineralized” as used herein refers to bone-derived elements possessing from about 8 to about 90 weight percent of their original inorganic mineral content and the expression “fully demineralized” as used herein refers to bone containing less than 8% of its original mineral context.

For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities of ingredients, percentages or proportions of materials, reaction conditions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding the numerical ranges and parameters set forth herein, the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a range of “1 to 10” includes any and all subranges between (and including) the minimum value of 1 and the maximum value of 10, that is, any and all subranges having a minimum value of equal to or greater than 1 and a maximum value of equal to or less than 10, for example, 5.5 to 10.

Reference will now be made in detail to certain embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the illustrated embodiments, it will be understood that they are not intended to limit the invention to those embodiments. On the contrary, the invention is intended to cover all alternatives, modifications, and equivalents that may be included within the invention as defined by the appended claims.

The headings below are not meant to limit the disclosure in any way; embodiments under any one heading may be used in conjunction with embodiments under any other heading.

I. Introduction

A delivery system for delivering therapeutic agents or materials to a surgical site is provided. In various embodiments, the delivery system comprises an implantable covering, for example a mesh bag, having at least two compartments configured to receive at least a first and a second therapeutic agent for delivery to a surgical site. The at least two compartments comprise top and bottom ends and sides defining, in several aspects, a cylindrical shape. At least one of the top or bottom ends define an opening configured to receive a removable filling member and having also a closing member. The removable filling member, for example a funnel, is utilized to fill at least one compartment with autograft material or another therapeutic agent. The covering provides a superior containment of the therapeutic agent, such as graft material, which helps focus and concentrate materials that provide healing at the surgical site. In some embodiments, the covering also helps the surgeon perform less invasive procedures, by delivering a contained unit of grafting material to the surgical site.

The delivery system described herein provides increased handling properties, ability to place grafting material reliably using minimally invasive procedures, and improved delivery characteristics such as graft retention compared with other systems. In some embodiments, upon placement, the covering facilitates transfer of the therapeutic agent and/or materials to the surgical site. In some embodiments, for example wherein the covering holds graft materials, the covering substantially prevents graft migration. The covering may participate in, control, or otherwise adjust, the release of the therapeutic agent from the covering or penetration of the covering by surrounding materials, such as cells or tissues.

The delivery system may be used to treat a wide variety of bone or soft tissue defects including surgically created or pre-existing (such as by trauma) defects. On some embodiments, the delivery system may be used to treat contained bony voids or contained defects. Such bony voids are voids or cavities that have a cortical shell on three sides. In some embodiments, the delivery system may be used to treat critical defects. Generally, critical defects are defects that will not heal spontaneously and must be grafted in order to assure healing. In some embodiments, the delivery system may be used to treat segmental defects. Segmental defects are defects in the cortical shaft of a long bone in which a segment is missing. In some embodiments, the delivery system may be used to treat contained or non-critical defects wherein the delivery system may act as a plug to assist healing. Other applications for the delivery system are discussed herein and none are intended to be limiting.

Generally, the covering may be at least a two compartment structure capable of at least partially retaining a therapeutic agent provided therein until the covering is placed at a surgical site. In some embodiments, the covering may be substantially non-expandable or minimally deformable. In some embodiments, the covering may be a temporary covering wherein the covering is substantially resorbable. For example, in some embodiments, the covering may be formed of a material that is substantially resorbed within 2 weeks, within 4 weeks, within 12 weeks, or within other suitable time frame. Accordingly, in some embodiments a delivery system including the covering may be a temporary delivery system. The covering may include one or more attachment mechanisms for retaining the covering at the surgical site. The attachment mechanism may be a mechanical attachment mechanism, a physical attachment mechanism, a biological attachment mechanism or a chemical attachment mechanism, or may employ combinations of these. The attachment mechanism may be used to attach the covering to skeletal or soft tissue proximate the surgical site.

In some embodiments, the covering may be used for containment of particulate or morselized materials (the therapeutic agent provided in the covering), optionally to provide a focus or concentration of biological activity. In some embodiments, the covering may be used for combining DBM particles and/or fibers with various bone grafting materials to achieve more effective mixing of these materials and contain them for delivery at the desired location. In various embodiments, bone grafting materials include one or more of bone particles, bone fibers, other osteoinductive or osteoconductive materials, BMP, antibiotics, or other materials.

In some embodiments, the covering may be used for maintaining materials (the therapeutic agents provided in the covering) in spatial proximity to one another, possibly to provide a synergistic effect upon mixing with each other. In some embodiments, the covering may be used to control availability of therapeutic agents provided within the covering to cells and tissues of a surgical site over time. In some embodiments, the covering may be used for delivery through a limited opening, such as in minimally invasive surgery or mini-open access. In some embodiments, the covering may be used to deliver morselized or particulated materials (the therapeutic agent provided in the covering) in pre-measured amounts. In other embodiments, the therapeutic agent may be liquid or flowable, or combinations of these with particulate, morselized, and/or other materials.

In various embodiments, the covering may contain a therapeutic agent such as a graft material. The covering limits, and in some embodiments eliminates, graft migration and maintains graft density. The delivery system, with contained therapeutic agent or material, may be configured to conform to surrounding bony contours or implant space. On some embodiments, the delivery system provides a pathway for healing/cell penetration and tissue ingrowth. Thus, the covering may facilitate transfer or diffusion of materials into and out of the covering. For example, the covering may facilitate diffusion from the covering of a therapeutic agent provided within the covering or may facilitate diffusion into the covering of materials in the surgical site, such as cells and tissues, into the covering. The covering may be configured to permit diffusion of some materials while substantially preventing diffusion of other materials. Further, in various embodiments, the covering may be configured such that diffusion is permitted into or out of certain portions of the covering but not other portions of the covering. In some embodiments, the covering may merely retain a therapeutic agent at the surgical site.

The covering may have at least two compartments or may have a plurality of compartments. Thus, in one embodiment, the covering is dual-compartment and comprises first and second compartments. A first therapeutic agent may be provided in the first compartment and no material or a second therapeutic agent may be provided in the second compartment. The second compartment may be adjacent to, apart from, inside, or surrounding the first compartment. In various embodiments, the at least two compartments are temporarily separated by separating members, for example drawstrings that can be pulled to allow the first and second therapeutic agents to mix prior to delivery at a surgical site.

Materials forming the first compartment and the second compartment may be the same or may be different. Selection of materials, positioning of the compartments, and other factors relating to the first and second compartments may be chosen to achieve simultaneous or sequential delivery or release of a therapeutic agent or therapeutic agents.

In various aspects, the biological environment for inducing new bone growth with DBM particles is optimized by allowing as many host osteogenic cells or growth factors adjacent to DBM particles. If a sufficient amount of proper live cells do not surround the DBM particles, they could easily be resorbed by macrophages and osteoclasts resulting in little to no new bone formation. The delivery systems described in the present disclosure include a mesh bag comprising separate compartments temporarily separated by drawstrings. Some of the compartments containing DBM are sealed closed at manufacture and some compartments can be empty with an opening into which local autograft particles can be placed. Once the autograft is added to an unfilled compartment, a flap attached to the empty compartment can be suture closed, the drawstrings can be removed by pulling at one end, thereby allowing the DBM particles and autograft particles to be thoroughly mixed inside the mesh bag. A funnel with a clip can be used to fill the empty compartment with autograft particles. In some embodiments, the clip can have a spring that can be temporarily attached to the bag and the funnel holds open the empty compartment to facilitate its filling with autograft particles. Other alternative delivery systems capable of achieving the thorough mixing of DBM particles and other therapeutic agents are also contemplated.

II. Covering Material

The covering may comprise a structural material and, in some embodiments, a functional material. The structural material may comprise a mesh material, a polymeric material, a substantially solid material, or other material. The functional material may comprise, for example, a radiopaque material, a bacteriocidal material, or other material.

Structural Material Characteristics

In various embodiments, in accordance with the specific application for which the covering is being used, the covering may be rigid, may be flexible, may be non-elastic, or may be elastic. The covering material may be braided, woven, non-woven shape memory, particulate, threaded, porous, non-porous, or substantially solid. While the term “structural” is used to describe the material forming the main structure of the covering, it is to be appreciated that this is not intended to imply that the covering need have structural or load-bearing characteristics.

The covering may participate in, control, facilitate, prevent, or otherwise adjust the release of the therapeutic agent. For example, the covering may act as a selectively permeable membrane and/or may be porous, with the level of porosity being related to the nature of the therapeutic agents inside the covering. Thus, the material for and configuration of the covering may be selected or adjusted based on desired release characteristics. Specific properties of the structural material that may be adjusted include thickness, permeability, porosity, strength, flexibility, elasticity, and others. It is to be appreciated that some of these properties may depend on others. For example, the thickness and porosity of the material may contribute to its strength, flexibility, and elasticity. In some embodiments, the covering may be made of a squishy, moldable, sticky, and/or tacky material to facilitate placement and packing of the covering.

In some embodiments, the covering may be porous to fluid and/or cells, may be biocompatible, and may be resistant to rupture (including should the therapeutic agent provided therein swell). In some embodiments, the covering with the therapeutic agent provided therein may be load-bearing. The covering may be resorbable or non-resorbable. The covering may provide increased handling properties, may have irrigation resistance, may have material retention characteristics, and/or may support cellular penetration. Flexibility of the covering may be selected to suit particular applications. In some applications, it may be desirable to have a flexible covering.

If the covering is made from a resorbable material, the covering degrades and disappears after a period of time. The covering thus may be considered a temporary covering. If the covering is not made of a resorbable material, the covering remains in the body. Tissue ingrowth may occur to bind the host tissue to the therapeutic agent provided within the covering. Tissue ingrowth through and around the covering, between the host tissue and the therapeutic agent provided within the covering, may be promoted via openings in the covering.

In various embodiments, the covering may comprise a porous material or a mesh material. The size of the pores of the covering may be designed to permit cellular infiltration (approximately several microns to several millimeters), but may also be designed specifically to exclude cells from the inside of the covering (e.g. approximately 0.45 microns) and only allow diffusion of small molecules (proteins and hormones). Thus, the covering may act to control access to the interior of the delivery system by cells. U.S. Patent Application Publication No. 2005/0283255 for Tissue-Derived Mesh for Orthopedic Regeneration describes suitable manners for forming a mesh for use with a covering as provided herein and is herein incorporated by reference in its entirety.

The covering may be formed of a resorbable or nonresorbable, natural or synthetic, biocompatible material. In some embodiments, more than one material may be used, including as multiple layers. For example, in an embodiment comprising two compartments, one or more materials may be used for the first compartment and a different material or materials may be used for the second compartment. For example, one compartment or portions thereof may be made of material or materials that provide a desired property or properties relative to other compartments or portions thereof, such as increased or decreased resorbability or stiffness, or the different compartments or portions thereof may be imparted with different drug delivery properties. Alternatively, all compartments may comprise the same material or mixtures of materials. Where the characteristics of the material are varied between compartments or over the surface of a single compartment, the pores of the first compartment or portion thereof may be larger than the pores of the second compartment.

The covering may comprise any suitable structure for delivering a therapeutic agent in vivo. Thus, as described, the covering may comprise a mesh. In other embodiments, the covering may comprise a polymeric structure with a chamber provided therein. The chamber may be filled with a therapeutic agent for delivering in vivo, such as autograft, demineralized bone matrix, or others disclosed herein.

In embodiments comprising more than one compartment, characteristics of the covering material may be varied between compartments. Generally, the porosity, flexibility, strength, or any other characteristic of one compartment may vary from that characteristic of the other compartment. Further, characteristics of the covering may vary at different positions of the covering regardless of compartmental configuration of the covering.

In some embodiments, the covering may expand when placed in the body. Expansion can be provided in at least two ways: the covering may be compressed such that the covering expands when placed in the body or the covering may be made of a material that expands when it comes in contact with water or other bodily fluids, either by way of liquid absorption, or by stretching when the materials inside it absorb liquid and themselves expand. In some embodiments, the covering may comprise a shape memory material such as copper-zinc aluminum-nickel alloy, copper-aluminum-nickel alloy, and nickel-titanium (NiTi) alloy. Reinforcing materials such as cortical bone, calcium phosphates, etc. may be incorporated into the structure of the covering to reinforce it. In other embodiments, the covering may be substantially non-expandable or minimally deformable.

The covering may be configured for specific compressive strength and rigidity by adjusting density and resorption time of the covering. In some embodiments, a coating may be provided over the covering. For example, the coating may be a compound of poly-L-lactide, of polyglycolic acid, or their polymers, or polyhydroxyalkanoates (polyhydroxybutyrates and polyhydroxyvalerates and copolymers). The coating may be selected such that it has a resorption time wherein it is resorbed by the body and the material within the covering is permitted to exit through openings in the covering.

A covering according to an aspect of the present application may comprise at least one of bioerodible polymers, bioabsorbable polymers, biodegradable biopolymers, synthetic polymers, copolymers and copolymer blends and combinations thereof. Exemplary materials may include biopolymers and synthetic polymers such as human skin, human hair, bone sheets, collagen, fat, thin cross-linked sheets containing fibers and/or fibers and chips, degradable sheets made from polyethylene glycol (PEG), chitosan sheets, alginate sheets, cellulose sheets, hyaluronic acid sheet, as well as copolymer blends of poly (lactide-co-glycolide) PLGA.

Advantageously, a covering according to an aspect of the present application utilizes polymer materials, which provide increased shelf life and further impart and/or improve moisture and/or radiation resistance. Accordingly, a covering provides improved stability, is resistant to environmental degradation, and provides increased durability to e.g., sterilization procedures.

Exemplary Covering Materials

Polymeric material (for example, see U.S. Pat. Nos. 6,696,073, 6,478,825, 6,440,444, and 6,294,187 and U.S. Patent Publications Nos. 2006/0216323 and 2005/0251267, all herein incorporated by reference in their entirety); woven material and braided material (for example, see U.S. Patent Publication No. 2005/0283255, herein incorporated by reference in its entirety); non-woven materials; shape memory material; porous materials; and non-porous materials may be used. In some embodiments, outer particles may be used to contain inner particles; particles may be attached to threads of material, and/or porosity may be added to mesh fibers. In some embodiments, materials may be used for portions of the covering, such as for a compartment of the covering, that are substantially impenetrable.

In some embodiments, the covering may comprise a mesh material. Suitable mesh materials include natural materials, synthetic polymeric resorbable materials, synthetic polymeric non-resorbable materials, and other materials. Natural mesh materials include silk, extracellular matrix (such as DBM, collagen, ligament, tendon tissue, or other), silk-elastin, elastin, collagen, and cellulose. Synthetic polymeric resorbable materials include poly(lactic acid) (PLA), poly(glycolic acid) (PGA), poly(lactic acid-glycolic acid) (PLGA), polydioxanone, PVA, polyurethanes, polycarbonates, polyhydroxyalkanoates (polyhydroxybutyrates and polyhydroxyvalerates and copolymers), polysaccharides, polyhydroxyalkanoates polyglycolide-co-caprolactone, polyethylene oxide, polypropylene oxide, polyglycolide-co-trimethylene carbonate, poly(lactic-co-glycolic acid), and others. Other suitable materials include carbon fiber, metal fiber, polyertheretherketones, non-resorbable polyurethanes, polyethers of all types, polyethylene terephthalte, polyethylene, polypropylene, Teflon, and various other meshes. In other embodiments, the covering may comprise non-woven material such as spun cocoon or shape memory materials having a coil shape or shape memory alloys. Alternatively, any of these materials may be used in a non-mesh form.

Generally, the covering may be formed of any natural or synthetic structure (tissue, protein, carbohydrate) that can be used to form a covering configuration. Thus, the covering may be formed of a polymer (such as polyalkylenes, for example, polyethylenes, polypropylenes), polyamides, polyesters, poly(glaxanone), poly(orthoesters), poly(pyrolicacid), poly(phosphazenes), polycarbonate, other bioabsorbable polymer such as Dacron or other known surgical plastics, a natural biologically derived material such as collagen, gelatin, chitosan, alginate, a ceramic (with bone-growth enhancers, hydroxyapatite), PEEK (polyether-etherketone), dessicated biodegradable material, metal, composite materials, a biocompatible textile (for example, cotton, silk, linen), extracellular matrix components, tissues, or composites of synthetic and natural materials, or other. Various collagen materials can be used, alone or in combination with other materials, including collagen sutures and threads. Some examples include polymer or collagen threads woven, or knitted, into a mesh. Other suitable materials include thin polymer sheets molded in the presence of a porogen and having underwent leaching; polymer sheets or naturally derived sheets such as fascia and other collagen materials, small intestinal submucosa, or urinary bladder epithelium, the sheets being punctured to introduce porosity; specific shapes printed using available or future printing technologies; naturally secreted materials such as bacterial cellulose grown within specific molds.

In some embodiments, mesh fibers may be treated to impart porosity to the fibers. This may be done, for example, to PLA, PLGA, PGA, and other fibers. One suitable method for treating the mesh fibers comprises supercritical carbon dioxide treatment to partially solubilize the particles. This treatment may further be carried out for viral inactivation. Another suitable method for treating the mesh fibers comprises explosive decompression. Explosive decompression generates porosity and leads to controlled permeability. The mesh material further may be loaded with cells, growth factors, or bioactive agents.

In further embodiments, fibers of a mesh material may be treated such as by having particles adhered thereto. The particles may be, for example, bone particles. Thus, in one embodiment, the covering may comprise a plurality of threads formed into a fabric. The threads may have particles adhered thereto. For example, the threads may have particles strung on the thread. In an alternative embodiment, the covering may be formed of a material and the material may be coated with particles.

In yet other embodiments, the covering may comprise a non-porous material, which may be permeable. A non-porous material may be used for later (or delayed) delivery of a therapeutic agent provided therein. Such therapeutic agent may comprise, for example, cells, growth factors, or bone morphogenetic proteins. Accordingly, in one embodiment, a delivery system for delayed delivery of cells, growth factors, or bone morphogenetic proteins is provided comprising a non-porous covering.

While certain embodiments are described with respect to having mesh characteristics, it is to be appreciated that not all embodiments may have such mesh characteristics. Further, the material used for the covering and its characteristics may be selected for specific applications. For example, in some embodiments, the covering may be formed of a resorbable material, such as formed as a resorbable container or capsule. Such resorbable material may be useful in delivering, for example, antibiotic to a site by an outer resorbable material, and then gradually exposing inner graft material after the infection is cleared. In such embodiments, the delivery system comprises a temporary delivery system.

Functional Material Characteristics

The covering material may have functional characteristics. Alternatively, other materials having functional characteristics may be incorporated into the covering. Functional characteristics may include radiopacity, bacteriocidity, source for released materials, tackiness. Such characteristics may be imparted substantially throughout the covering or at only certain positions or portions of the covering.

Suitable radiopaque materials include, for example, ceramics, mineralized bone, ceramics/calcium phosphates/calcium sulfates, metal particles, fibers, iodinated polymer or mixtures thereof. Other techniques for incorporating a biocompatible metal or metal salt into a polymer to increase radiopacity of the polymer may also be used. Suitable bacteriocidal materials may include, for example, trace metallic elements. In some embodiments, trace metallic elements may also encourage bone growth.

Functional material, such as radiopaque markers, may be provided at one or more locations on the covering or may be provided substantially throughout the covering. Thus, for example, in a tubular covering, a radiopaque marker may be provided at a tip of the tubular covering. Such marker may facilitate placement of the covering. Radiopaque materials may be incorporated into the covering and/or into the therapeutic agent for delivery by the covering. Further, radiopaque materials may be provided at only some locations on the covering such that visualization of those locations provides indication of the orientation of the covering in vivo.

The covering itself may be designed to release materials during degradation of the covering material. Thus, bone morphogenic proteins (BMPs), growth factors, antibiotics, angiogenesis promoting materials (discussed more fully below), bioactive agents (discussed more fully below), or other actively releasing materials may be incorporated into the covering material such that as the covering material is degraded in the body, the actively releasing material is released. For example, an actively releasing material may be incorporated into a biodegradable polymer covering such as one manufactured of a biodegradable polyester such as poly(lactic acid) (PLA), poly(glycolic acid) (PGA), poly(lactic-co-glycolic acid) (PLGA), or polyhydroxyalkanoates (polyhydroxybutyrates and polyhydroxyvalerates and copolymers). In some embodiments, poly(ethylene glycol) (PEG) may be incorporated into the biodegradable polyester to add hydrophilic and other physico-chemical properties to enhance drug delivery. In some embodiments, composites of allograft bone and biodegradable polymers (for example, PLEXUR™ products available from Medtronic) may be used in the covering.

In some embodiments, the covering may comprise a material that becomes tacky upon wetting. Such material may be, for example, a protein or gelatin based material. Tissue adhesives, including mussel adhesive proteins and cryanocrylates, may be used to impart tackiness to the covering. In further examples, alginate or chitosan material may be used to impart tackiness to the covering. In further embodiments, an adhesive therapeutic agent or material may be placed on a portion of the covering or in a particular region of the covering to anchor that portion or region of the covering in place at an implant site.

In one embodiment of a covering comprising two compartments, first and second materials may be used for the first and second compartments, respectively. The first material may release or expose a growth factor according to a first rate and the second material may release a growth factor according to a second rate. Further, the growth factors released by the first and second compartments may be the same or may be different. For example, an angiogenic growth factor may be provided with the first compartment and an osteoinductive growth factor may be provided with the second compartment.

Mesh Formulation

Any suitable technique may be used for forming a material for the covering. Generally, the material may be formed as a substantially solid material, as a sheet, as a mesh, or in other configuration. In some embodiments, the material may be a textile type material. Thus, for example, the material may be formed using a textile approach such as be weaving, rug making, knitting. Such formation may be by a mechanical or industrial method. In another embodiment, a substantially solid sheet may be formed and may be treated to assume a configuration penetrable by cells, fluids, and proteins. For example, the sheet may be perforated, may be expanded to create openings, or other. Also, it would be perfectly suitable to take a thin sheet of the covering material, and to perforate it, expand it to create openings, or otherwise make it penetrable by cells, fluids and proteins.

In one embodiment, elongated bone-derived particles or fragments of small intestinal submucosa may be combined longitudinally into three small bundles, each having, for example, from about 1 to about 3 tissue particles. The three bundles may then be braided. Various methods of braiding and types of braids any of which may be useful in producing the material of the invention herein are also described, for example, by Shaw, KNOTS—Useful & Ornamental, Bonanza Books, New York (1983), incorporated herein by reference. The ends of the braided tissue-derived particles may then be glued together using a fixation agent to prevent their unraveling, or they may be held together with a biocompatible polymer or metal band.

In an alternative embodiment, bone-derived particles are combined with a solvent to form a material. Exemplary solvents include water, lower alkanols, ketones, and ethers and mixtures of any of these or other materials. The material may then be extruded at an appropriate temperature and pressure to create a thread. Threads may also be produced by spinning, drawing, rolling, solvent-extruding, cutting or laser cutting from a sheet or bar stock. The material may alternatively be cast or molded into a solid sheet or bar stock and then cut into thin threads. These may be used immediately or woven into a mesh. Alternatively or in addition, they may be spliced, wrapped, plied, cabled, braided, woven, or some combination of these. The material may be shaped by thermal or chemical bonding, or both. In one embodiment, a portion of the solvent is removed from the material before extrusion.

Alternatively or in addition, the material may be cast as a slurry, extruded, or molded. A variety of materials processing methods will be well known to those skilled in the art. For example, the material may be solvent cast using a press such as a Carver press to spread the material into a film. Solvent evaporation will yield a porous film. Alternatively, the material may be compression molded into a film. The mesh size or porosity of the film will depend on the thickness of the film and the viscosity of the precursor and can be easily manipulated by one skilled in the art. Where elongated particles are used in an extruded aggregate, they will tend to be aligned roughly parallel to one another.

In an alternative embodiment, a thread of a biocompatible natural or synthetic material, for example, polylactide or collagen, may be coated with tissue-derived or other elements, for example, by dubbing. For example, a polymer fiber may be coated with an adhesive, for example, lecithin, and bone particles or other osteoconductive or osteoinductive fibrils allowed to adhere to the thread. The thread may then be twisted on itself or with a second or a plurality of similarly treated threads. Alternatively or in addition, the threads may be braided. The adhesive may be a lipid that is waxy at room temperature, for example, a di- or tri-glyceride that is solid at room temperature. Alternatively or in addition, the adhesive may be a phosphocholine or phosphatidylcholine. In some embodiments, the adhesive is a material that binds both the thread and the material that is used to coat the thread (e.g., bone particles) but that does not degrade either. Non-aqueous adhesives may improve the stability of the final aggregate as compared to aqueous adhesives.

Suitable fibers may be formed utilizing well known techniques, including braiding, plying, knitting, weaving, felting, that are applied to processing natural fibers, for example, cotton, silk, and synthetic fibers made from synthetic bioabsorbable polymers, such as poly(glycolide) and poly(lactic acid), nylon, cellulose acetate. See, Mohamed, American Scientist, 78: 530-541 (1990). In some embodiments, collagen thread is wound onto cylindrical stainless steel spools. The spools are then mounted onto the braiding carousel, and the collagen thread is then assembled in accordance with the instructions provided with the braiding machine. In one particular run, a braid was prepared of four collagen threads, which consisted of two threads of non-crosslinked collagen and two threads of crosslinked collagen. One skilled in the art will recognize that these techniques may be applied to the other fibrous materials described herein.

Fibers and more evenly dimensioned particles may also be plied into yarns using the same methods and same machinery known to those skilled in the art in plying threads made out of other material, such as cotton, polyester. Four collagen threads were twisted together. Three of the resultant 4-ply strands were then twisted together in the opposite direction, and then 5 of the resultant 12 ply strands were twisted in the opposite direction.

Elongated materials including multistranded materials, for example braids, plied yams, cables, may be knitted into tubular or flat fabrics by using techniques known to those skilled in the art of producing fabrics manufactured from other types of threads. Various biologically active therapeutic agents can be incorporated in, or associated with, the braided, knitted, or woven materials. Particles and fibers and materials of these (including multistranded materials) may alternatively or additionally be assembled into a material by non-woven methods such as laying, needle-punching, and hooking (as for a rug). For example, a thread may be attached to another thread or a pressed film.

Regardless of the assembly method, the material shape, mesh size, cable thickness, and other structural characteristics, such as architecture, may be customized for the desired application. For example, where a two dimensional aggregate is used to retain a thixotropic material within a gap, a tight weave is preferred to prevent leakage. To optimize cell or fluid migration through the mesh, the pore size may be optimized for the viscosity and surface tension of the fluid or the size of the cells. For example, pore sizes on the order of approximately 100-200 μm may be used if cells are to migrate through the mesh. Mesh size may be controlled by physically weaving strands of the material by controlling the ratio of solvent to solids in a precursor material.

Cells may be seeded onto the material, or contained within it. In one embodiment, cells may be encapsulated in a matrix such as alginate or collagen gel and the capsules placed on the material. Seeded materials generally do not need to be incubated for long periods of time in solutions that could partially dissolve the binding agent. Instead, the capsules may be placed on the material or covering shortly before implantation. In another embodiment, cells are simply mixed with a gel which is then combined with the material. Alternatively, a material or covering may be cultured with cells before implantation. In one embodiment, thicker materials are used for culturing to increase mechanical integrity during implantation. Any class of cells, including connective tissue cells, organ cells, muscle cells, nerve cells, and stem cells, may be seeded onto the implant. In an exemplary embodiment, connective tissue cells such as osteoblasts, osteoclasts, fibroblasts, tenocytes, chondrocytes, and ligament cells and partially differentiated stem cells such as mesenchymal stem cells and bone marrow stromal cells are employed.

III. Covering Configuration or Form

The shape, configuration, or form of the covering may be selected for particular applications. Such shape and configuration may include, for example, the basic shape of the covering (for example, a cylinder or a bag), whether the covering has a single or a plurality of compartments, and whether the covering includes attachment mechanisms. The covering (or delivery system) may be configured to conform to surrounding bony contours of the space in which it is placed.

Form

In various embodiments, the covering may be formed of as a mesh and may comprise a woven material. The woven material may have varying degrees of permeability. It may be permeable, semi-permeable, or non-permeable. Permeability may be with respect to cells, to liquids, to proteins, to growth factors, to bone morphogenetic proteins, or other. In further embodiments, the material may be braided.

In alternative embodiments, the covering may comprise a substantially solid structure, such as a polymer structure with a chamber, or a spun cocoon.

Shape

The covering may have any suitable configuration. For example, the covering may be formed as a ring, a cylinder, a cage, a rectangular shape, a mesh, a suture-like wrap, a continuous tube, or other configuration. In specific embodiments, the covering may be formed as a thin tube designed to be inserted through catheters or an introducer tube, a rectangular shape designed to fit adjacent to spinal processes for posterolateral spine fusion, a cube like structure designed to fit between vertebral bodies or within cages for interbody spinal fusion, a tube-like shape where the ends are designed to be fitted onto nonunion long bone defects, relatively flat shapes designed to fill cranial or maxillofacial defects, rectangular structures designed for osteochondral defects, structures pre-shaped to fit around various implants (for example, dental, doughnut with hole for dental implants), or relatively elastic ring-like structures that will stretch and then conform to shapes (for example, rubber band fitted around processes). In an embodiment wherein the covering is formed as a cage, the cage may comprise a plurality of crossed filaments which define between them a series of openings for tissue ingrowth. Any of these shapes may be used for a covering comprising a plurality of compartments. For example, in a tubular embodiment, the tube may be formed into a plurality of compartments by tying a cord around the tube at one or more points, or by other suitable mechanism such as crimping, twisting, knotting, stapling, sewing, or other. The configuration of the covering may be determined by the therapeutic agent to be provided within the covering. For example, if the therapeutic agent to be contained comprises fibers, the covering may be formed as strings or sutures that are wrapped around the fibers.

In certain embodiments, a bone void can be filled. A compartment within the covering material can be at least partially filled with a bone repair substance. In various embodiments, at least partially filled as used herein, can mean that a percentage of the volume of a compartment (or covering material, as applicable) is at least 70% occupied, at least 75% occupied, at least 80% occupied, at least 85% occupied, at least 90% occupied, at least 95% occupied, or 100% occupied. The covering material can be inserted into an opening in the defect until the defect is substantially filled. In various embodiments, a substantially filled as used herein can mean that a percentage of the volume of a defect (or covering material, as applicable) is at least 70% occupied, at least 75% occupied, at least 80% occupied, at least 85% occupied, at least 90% occupied, at least 95% occupied, or 100% occupied. The excess material extending beyond the surface of the bone if the bone were without the defect can then be removed, or at least partially removed such that the opening of the defect is flush with the uninjured bone surface.

In some embodiments, the covering may be labeled. Such labeling may be done in any suitable manner and at any suitable location on the covering. In some embodiments, labeling may be done by using a silk screen printing, using an altered weaving or knotting pattern, by using different colored threads, or other. The labeling may indicate information regarding the covering. Such information might include part number, donor id number, number, lettering or wording indicating order of use in the procedure or implant size.

Compartments

Osteogenic material delivery systems in accordance with embodiments discussed in this disclosure are depicted in FIGS. 1, 2 and 3. In some embodiments, as shown in FIG. 1, delivery system 100 comprises covering 102 having an elongated containment portion 104 separated into three compartments 106, 108 and 110 for housing therapeutic agents for delivery to a surgical site. Situated side by side, compartments 106, 108 and 110 are separated from each other by first and second separation members 116, 118. Elongated containment portion 104 also includes a length, width and height or cross section which may vary depending on the application for covering. The cross section can be tubular or cylindrical and in alternative embodiments, any cross-sectional shape, such as a generally circular, oval, rectangular, generally square, generally star, or any other suitable shape may be used. In the embodiments shown in FIGS. 1, 2, and 3 the coverings 102, 202 and 302 comprise a mesh material and the delivery systems 100, 200 and 300 can be a mesh bag. Within these coverings or mesh bags, there is provided a particulated therapeutic agent such as milled bone or DBM particles/fibers, wherein the ratio of DBM fibers to DBM chips is about 30:60.

Containment portion 104 also contains top and bottom ends 112, 114. As further depicted in FIG. 1, in some embodiments, compartments 106 and 110 are enclosed and there is provided a particulate therapeutic agent such a milled bone or DBM particles/fibers. Compartment 108 can be left empty or it can be partially or completely filled with autograft particles. In one embodiment, at top end 112, compartment 108 defines an opening 120 which can be sealed closed by a closing member 122. Closing member 122 can be a flap sealable by suturing, heating, using adhesives, solvent treatment, knotting, using interference, friction fits or any other means.

In various embodiments, separation members 116 and 118 temporarily separate compartments 106 and 110 from 108. While compartments 106 and 110 can contain DBM and are sealed closed, compartment 108 can be empty. At opening 120, compartment 108 is configured to receive a filling member 400, which, as illustrated in FIG. 4, can be a funnel.

In various embodiments, the covering may be configured to facilitate placement of graft material therein. For example, in FIG. 1, temporary separation members 116 and 118 can be completely removed to allow for mixing of the materials present in all three compartments prior to insertion at a surgical site. In some aspects, compartment 108 can be left unfilled or it can be partially or completely filled either with autograft and/or growth factors thereby increasing the exposure of DBM particles/fibers to osteogenic cells and allowing the DBM cytokines to signal the autologous osteogenic cells to begin forming new bone to boost the osteoactivity of the weakly osteoinductive DBM already present in covering 102.

In other aspects, as shown in FIG. 2, delivery system 200 contains a covering 202 having temporary separation members or pull strings 216 and 218 which can be partially pulled to create three cylindrically shaped side by side compartments 206, 208 and 210 shown as generally circular compartments in a top view. In some embodiments, as illustrated in FIG. 2, compartment 208 is left empty, but upon pulling strings 216, 218, the volume of covering 202 can decrease or shrink (e.g., reduce in size, or make compact), allowing the surgeon flexibility to fashion covering 202 as required for a specific surgical site. In other aspects, compartment 208 can be filled with autograft or other desirable additives.

With further reference to FIG. 1, as pull strings 116 and 118 are removed, the bone graft material in compartment 108 is forced to mix with, surround and coat the DBM particles/fibers so that bone formation can be induced throughout the graft rather than just along the surface of the DBM containing mesh bag. This is allows live cells and/or growth factors to contact the DBM particles and induce bone growth throughout the complete graft rather than just along the surface of the DBM containing mesh bag or covering.

FIG. 3 is a side view of another embodiment of a delivery system 300 having a covering 302 containing two side by side compartments 306 and 308 separated by separation member 316, in this embodiment a pull string. Compartment 308 can be unfilled or partially filled either as manufactured or as subsequently filled at a surgical site. Compartment 308 is sealed closed at bottom end 314 but forms an opening 320 at top end 312. After filling compartment 308, opening 320 can be sealed with closing member 322, which, in one aspect can be a flap. Opening 320 is configured to receive filling member 400 as illustrated in FIG. 4. Opening 320 defines a mating surface 324 which is configured to receive mating surface 454 defined by opening 453 of filling member 400.

FIG. 4 depicts a side view of filling member 400, which in some aspects, is a funnel. The funnel has a head portion 450 and a neck portion 452 defining an opening 453 and a mating surface 454 configured to mate with mating surface 324 of compartment 308 or mating surface 124 of compartment 108 of covering 102 depicted in FIG. 1. Generally, it is contemplated that circumferences 456 and 458 are sufficient in size to enable funnel 400 to receive allograft chips and other graft material to allow for the filling of covering compartment 108 of covering 102 or compartment 308 of covering 302 either by gravity or with the help of a plunger. Additionally, it is contemplated that the head and neck of funnel 400, both include wider or narrower funnel shape configurations as would generally occur to one skilled in the art to perform its load assisting function. Filling member 400 also comprises an attachment member 460. In some embodiments, attachment member 460 can be a clip having a spring 462, which allows funnel 400 to be temporarily attached to the mesh bag. Other attachment members such as friction or interference fittings are also contemplated.

In other embodiments, the filling member utilized to fill empty compartments can be a spoon or a syringe or any other means that can adequately perform a compartment loading function. In some embodiments, the filling member (e.g., funnel) can contain channels for suturing the filling member to the cover (e.g., bag). After the covering is filled with material, the suture can be cut and the filling member removed.

In the embodiments shown in FIGS. 1 and 3 both ends 112 and 114, 312 and 314, or sides 113 and 115, 313 and 315, respectively can be sealed either self sealed or sealed by heat, adhesion or stitches. One or both ends or sides may contain an attachment or coupling mechanism (not shown) to attach the covering to skeletal or soft tissue proximate to a surgical site. Any suitable attachment mechanism can be used, such as a tab, loop, tack or other structure adapted for attachment at the site. Also, for example, a covering may include a hook-and-eye (Velcro) portion.

In various embodiments, the materials for each compartment may have different release profiles, different porosities, and other different characteristics. Selection of materials, positioning of the compartments, and other factors relating to the first, second or third compartments may be chosen to achieve simultaneous or sequential delivery or release of a therapeutic agent or therapeutic agents. For example, a first therapeutic agent may be provided in the first compartment, a second therapeutic agent may be provided in the second compartment and a third therapeutic agent may be provided in the third compartment. In some embodiments, an osteoinductive therapeutic agent may be placed in a compartment generally adjacent tissue being treated as implanted and an osteoconductive therapeutic agent may be placed in a compartment not adjacent tissue being treated. Release rates for the materials provided in a first compartment, and second compartment may be different from each other and from the material placed in a third compartment. In some embodiments as illustrated in FIGS. 1 to 3, at least one of the compartments may be unfilled at the time of surgery and autograft or other material may be provided therein in the operating room or at the surgical site.

As in embodiments illustrated in FIGS. 1, 2 and 3, the materials for each compartment shown in these figures may have different release profiles, different porosities, and other different characteristics. Selection of materials, positioning of the compartments, and other factors relating to the first, second or third compartments may be chosen to achieve simultaneous or sequential delivery or release of a therapeutic agent or therapeutic agents. For example, a first therapeutic agent may be provided in the first compartment, a second therapeutic agent may be provided in the second compartment and a third therapeutic agent may be provided in the third compartment.

For multi-compartment coverings, the covering may be closed after filling the compartments with the desired therapeutic agents. Further, the covering may be left substantially open with one or more unsealed ends. Accordingly, the covering may be provided in an unfilled, unsealed state. After a therapeutic agent for delivery is placed in the covering, the covering may be permanently or temporarily closed. Permanent closure may be, for example, by heat sealing, stitching, adhesion, or other methods. Temporary closure may be by tying, fold lock, or cinching. A temporarily closed covering can be opened without damaging to the covering during surgical implantation to add or remove therapeutic agents in the covering.

In some embodiments, at least one but not all of the compartments may be weight-bearing. In other embodiments, all of the compartments may be weight-bearing.

In one embodiment, the covering may comprise a penetrable material at a first compartment configured for placement adjacent bone and a substantially impenetrable material at a second compartment configured for placement adjacent soft tissue. Alternatively, the material of the compartments may have substantially identical characteristics. The covering then can be positioned in any desirable manner. By way of example only, a covering may have a porous surface that is positioned adjacent bone, and a separate or opposite surface that has a generally impenetrable surface that is positioned adjacent soft tissue. Alternatively, a covering may have one compartment that comprises a porous material, and a second compartment that comprises a substantially impenetrable material.

Attachment Mechanisms

The covering may be implanted directly at, near or in the bone defect or optionally be configured with structures to permit attachment at the surgical site, such as to skeletal tissue or to soft tissue structures, or for attachment to other coverings, or for attachment to adjacent implantable medical devices or products (such as a rod or screw or cross-brace of a pedicle screw fixation system, a hip prosthesis, a bone plate, and the like). Generally, the attachment mechanism may be used to retain the covering at the surgical site and any mechanisms capable of doing so may be used. The attachment may be to bone or to adjacent tissues such as muscle, tendon, or ligament. In some embodiments, the attachment mechanism can be made from a biodegradable polymer that is the same or different material than the covering.

Where the covering retains a bone graft substance, the covering may be held in a relatively stable position relative to bone (or relative to the surgical site or surgical defect) to promote bone growth. Accordingly, in some embodiments, the delivery system may be suitable for assisting in attaching tendons, artificial tendons, or ligaments to bone or other structure.

The bone or soft tissue to which the covering is attached may be prepared for receiving the attachment mechanism(s). For example, in spinal applications, slots or perforations may be provided in posterior elements such as transverse processes, spinous processes, or other bone or tissue to receive the attachment mechanism.

Any suitable attachment mechanism may be used, including mechanical, physical, chemical, and biological attachment mechanisms. The attachment mechanism may be provided at an end of the covering, centrally in or on the covering, generally in or on the body of the covering, or any combinations of these. When an attachment mechanism is used to couple first and second coverings to one another, such attachment or coupling may be done pre-implantation or post-implantation. In post-implantation embodiments, the coupling may be done by inserting first and second coverings through an opening into a space and coupling the coverings within the space. In some embodiments, the covering may be provided with attachment mechanisms to facilitate suturing or other attachment of the covering in vivo.

In some embodiments, a covering may include an area for receipt of an attachment mechanism. For example, a covering may include a tab for receipt of a screw. In other embodiments, an attachment mechanism may interface with any portion of the covering. For example, a screw attachment mechanism may be threaded through a covering at any location, including central to a containment area of the covering. In some embodiments, a screw attachment mechanism may be threaded through the covering and the substance provided in the containment area of the covering.

A further method of attachment may comprise suturing or otherwise attaching the covering to a tether, anchor, or screw embedded in a bony structure, e.g. a pedicle screw of a spinal stabilization system. Such screw, anchor, or tether may pass through the covering and its contained contents to provide fixation, or through a tab at a margin of the covering, or through other structure of the covering.

Chemical attachment mechanisms may comprise, for example, a bioadhesive or glue, cement, tape, tissue adhesives, or similar mechanism. Chemical attachment mechanisms may further comprise mechanisms that facilitate cross-linking. In further embodiments, attachment mechanisms such as crimping, welding, soldering, or brazing may be used. For example, tissue welding may be used. Further, attachment may be achieved via friction.

Suitable adhesives for use may include, for example, cyanoacrylates (such as histoacryl, B Braun, which is n-Butyl-2 Cyanoacrylate; or Dermabond, which is 2-octylcyanoacrylate); epoxy-based compounds, dental resin sealants, dental resin cements, glass ionomer cements, polymethyl methacrylate, gelatin-resorcinol-formaldehyde glues, collagen-based glues, inorganic bonding agents such as zinc phosphate, magnesium phosphate or other phosphate-based cements, zinc carboxylate, L-DOPA (3,4-dihydroxy-L-phenylalanine), proteins, carbohydrates, glycoproteins, mucopolysaccharides, other polysaccharides, hydrogels, protein-based binders such as fibrin glues and mussel-derived adhesive proteins, and any other suitable substance. Adhesives may be selected for use based on their bonding time; e.g., in some circumstances, a temporary adhesive may be desirable, for example, for fixation during the surgical procedure and for a limited time thereafter, while in other circumstances a permanent adhesive may be desired. Where the compartment is made of a material that is resorbable, the adhesive can be selected that would adhere for about as long as the material is present in the body. In some embodiments, the covering material may be treated to form chemical linkages between the covering and adjacent tissue, whether bone or soft tissue.

In some embodiments, biological attachment may be via mechanisms that promote tissue ingrowth such as by a porous coating or a hydroxyapatite-tricalcium phosphate (HA/TCP) coating. Generally, hydroxyapatite bonds by biological effects of new tissue formation. Porous ingrowth surfaces, such as titanium alloy materials in a beaded coating or tantalum porous metal or trabecular metal may be used and facilitate attachment at least by encouraging bone to grow through the porous implant surface. These mechanisms may be referred to as biological attachment mechanisms.

In some embodiments, the covering can comprise edges having polymers that are more hydrophilic than the polymers in other areas of the covering (e.g., body). In this embodiment, the covering, when implanted, will draw bodily fluid to this area more so than in other areas and this will cause the edges of the covering to expand and anchor the covering at, near or in the defect site. Alternatively, the body of the covering can have polymers that are more hydrophilic than the polymers in the edges of the covering. In this embodiment, the covering, when implanted, will draw bodily fluid to the body area more so than the edges and this will cause the body of the covering to expand and anchor the covering at, near or in the defect site.

Generally, any combination of mechanical, physical, chemical, or biological attachment mechanisms may be used.

Any of the various attachment mechanisms may be provided as part of the covering or may be supplied separately. In various embodiments, the attachment mechanisms may be integral to the covering. Alternatively, the attachment mechanisms may be secured to the covering, for example, by stitching, welding, crimping, or other. The attachment mechanisms may have any suitable geometric configuration and may optionally include apertures for receiving other components for coupling in vivo, such as an aperture for receiving a screw. Thus, for example, an attachment mechanism may be provided configured for receiving an anchor for fixation to bone. Generally, any number of attachment mechanisms may be provided at any suitable location on the covering.

The attachment mechanisms may be manufactured of the same material as the portion of the covering to which it is coupled or may be manufactured of a different material from the portion of the covering to which it is coupled. The attachment mechanism may be resorbable or nonresorbable. The material of the attachment mechanism may be selected to allow anchoring the covering to an adjacent covering having a complementary attachment mechanism or to another structure. In various embodiments, the attachment mechanism may comprise, allograft, synthetic materials, demineralized bone, nondemineralized bone, other material, or combinations of these. The shape and size of the attachment mechanism may be selected based on application.

In some embodiments, the covering may be tubular and have threaded ends such that the ends may be threaded with a reciprocal thread of a further device or implant. For example, the covering may be used with interference screws. In some embodiments, the covering may include extensions or tabs that may be used for wrapping around or suturing to the surgical site. Alternatively, the covering may be sutured directly to the surgical site. The ends of the covering may be presealed or may be sealed after introduction of contents. Sealing may be done by using adhesives, heating, solvent treatment, suturing, knotting, or any other means.

Packing

The therapeutic agent may be packed in the covering at any suitable density. For some applications, the therapeutic agent may be loosely packed in the covering to enhance manipulability. In some embodiments, the material may be packed in the covering such that the covering retains flexibility and may be folded over itself. In other applications, the therapeutic agent may be tightly packed in the covering to provide a relatively stiff delivery system, and it may be weight bearing. In some embodiments, the covering may be configured to facilitate placement of graft material in the covering as was illustrated in FIGS. 1-3 described herein.

IV. Therapeutic agents for Delivery by Covering

A substance is provided inside the covering, before or during surgery (as described below), for delivery in vivo. Generally, the substance or material may be homogenous or heterogeneous. The substance or material may be selected to exhibit certain gradients. For example, the substance or material may be selected to exhibit a gradient to guide, lure, or attract cells along a pathway. Such gradient may comprise a cell gradient, a cell type gradient (for example transitioning from bone cells to cartilage cells or transitioning from bone cells to tendon cells), a gradient of conductivity, or a gradient of density/porosity. In some embodiments, the substance or material may comprise a sequence of ingredients.

The covering may be used to deliver a substance comprising any suitable biocompatible material. In specific embodiments, the covering may be used to deliver surface demineralized bone chips, optionally of a predetermined particle size, demineralized bone fibers, optionally pressed, and/or allograft. For embodiments wherein the substance is biologic, the substance may be autogenic, allogenic, xenogenic, or transgenic. Other suitable materials that may be positioned in the covering include, for example, protein, nucleic acid, carbohydrate, lipids, collagen, allograft bone, autograft bone, cartilage stimulating substances, allograft cartilage, TCP, hydroxyapatite, calcium sulfate, polymer, nanofibrous polymers, growth factors, carriers for growth factors, growth factor extracts of tissues, demineralized bone matrix, dentine, bone marrow aspirate, bone marrow aspirate combined with various osteoinductive or osteoconductive carriers, concentrates of lipid derived or marrow derived adult stem cells, umbilical cord derived stem cells, adult or embryonic stem cells combined with various osteoinductive or osteoconductive carriers, transfected cell lines, bone forming cells derived from periosteum, combinations of bone stimulating and cartilage stimulating materials, committed or partially committed cells from the osteogenic or chondrogenic lineage, or combinations of any of the above. In some embodiments, the substance may be pressed before placement in the covering. A substance provided within the covering may be homogenous, or generally a single substance, or may be heterogeneous, or a mixture of substances.

In some embodiments, the covering can comprise one or more compartments having demineralized bone material therein. The demineralized bone material can be comprise demineralized bone, powder, chips, triangular prisms, spheres, cubes, cylinders, shards, fibers or other shapes having irregular or random geometries. These can include, for example, “substantially demineralized,” “partially demineralized,” or “fully demineralized” cortical and cancellous bone. These also include surface demineralization, where the surface of the bone construct is substantially demineralized, partially demineralized, or fully demineralized, yet the body of the bone construct is fully mineralized. In some embodiments, the covering may comprise some fully mineralized bone material. The configuration of the bone material can be obtained by milling, shaving, cutting or machining whole bone as described in for example U.S. Pat. No. 5,899,939. The entire disclosure is herein incorporated by reference into the present disclosure.

In some embodiments, the covering comprises elongated demineralized bone fibers having an average length to average thickness ratio or aspect ratio of the fibers from about 50:1 to about 1000:1. In overall appearance the elongated demineralized bone fibers can be in the form of threads, narrow strips, or thin sheets. The elongated demineralized bone fibers can be substantially linear in appearance or they can be coiled to resemble springs. In some embodiments, the elongated demineralized bone fibers are of irregular shapes including, for example, linear, serpentine or curved shapes. The elongated bone fibers can be demineralized however some of the original mineral content may be retained when desirable for a particular embodiment.

In some embodiments, the covering comprises elongated demineralized bone fibers and chips. In some embodiments, the ratio of fibers to chips or powders is from about 5, 10, 15, 20, 25, 30, 35, 40, or 45 fibers to about 30, 35, 40, 45, 50, 55, 60, 65, or 70 chips.

In some embodiments, the biocompatible material comprises demineralized bone matrix fibers and demineralized bone matrix chips in a 30:60 ratio.

In some embodiments, the demineralized bone material can be in the covering and comprises from about 1 to about 70 micrometers particle size range or from about 125 to about 250 micrometer particle size range.

In some embodiments, the covering may have a modulus of elasticity in the range of about 1×10² to about 6×10⁵ dynes/cm², or 2×10⁴ to about 5×10⁵ dynes/cm², or 5×10⁴ to about 5×10⁵ dynes/cm². After the cover is administered to the target site, the covering may have a modulus of elasticity in the range of about 1×−10² to about 6×10⁵ dynes/cm², or 2×10⁴ to about 5×10⁵ dynes/cm², or 5×10⁴ to about 5×10⁵ dynes/cm².

In some embodiments, the substance may be designed to expand in vivo. Such an embodiment may be used to fill a space and create contact with congruent surfaces as it expands in vivo, for example for interbody fusion. Thus, in some embodiments, the delivery system may be used in the disc space, between implants, or inside a cage.

The covering retains the substance in place by pressure against the covering. The covering thus may, in some embodiments, maintain particles of substance in close proximity (for example, where the covering retains a substance comprising bone particles). Generally, the ratio of covering material to substance for placement within the covering may be low. For example, in some embodiments, the ratio of covering material to substance, by weight, may be approximately 1:1,000, 1:100, 1:50, 1:25, 1:1, or any suitable ratio that may be higher or lower than these.

In some embodiments the substance delivered by the covering may include or comprise an additive such as an angiogenesis promoting material or a bioactive agent. It will be appreciated that the amount of additive used may vary depending upon the type of additive, the specific activity of the particular additive preparation employed, and the intended use of the composition. The desired amount is readily determinable by one skilled in the art. Angiogenesis may be an important contributing factor for the replacement of new bone and cartilage tissues. In certain embodiments, angiogenesis is promoted so that blood vessels are formed at an implant site to allow efficient transport of oxygen and other nutrients and growth factors to the developing bone or cartilage tissue. Thus, angiogenesis promoting factors may be added to the substance to increase angiogenesis. For example, class 3 semaphorins, for example, SEMA3, controls vascular morphogenesis by inhibiting integrin function in the vascular system, and may be included in the recovered hydroxyapatite.

In accordance with some embodiments, the substance may be supplemented, further treated, or chemically modified with one or more bioactive agents (also referred to as therapeutic agents) or bioactive compounds (also referred to as therapeutic compounds). Bioactive agent or bioactive compound, as used herein, refers to a compound or entity that alters, inhibits, activates, or otherwise affects biological or chemical events. For example, bioactive agents may include, but are not limited to, osteogenic or chondrogenic proteins or peptides; demineralized bone powder; collagen, insoluble collagen derivatives, etc., and soluble solids and/or liquids dissolved therein; anti-AIDS substances; anti-cancer substances; antimicrobials and/or antibiotics such as erythromycin, bacitracin, neomycin, penicillin, polymycin B, tetracyclines, biomycin, chloromycetin, and streptomycins, cefazolin, ampicillin, azactam, tobramycin, clindamycin and gentamycin, etc.; immunosuppressants; anti-viral substances such as substances effective against hepatitis; enzyme inhibitors; hormones; neurotoxins; opioids; hypnotics; anti-histamines; lubricants; tranquilizers; anti-convulsants; muscle relaxants and anti-Parkinson substances; anti-spasmodics and muscle contractants including channel blockers; miotics and anti-cholinergics; anti-glaucoma compounds; anti-parasite and/or anti-protozoal compounds; modulators of cell-extracellular matrix interactions including cell growth inhibitors and antiadhesion molecules; vasodilating agents; inhibitors of DNA, RNA, or protein synthesis; anti-hypertensives; analgesics; anti-pyretics; steroidal and non-steroidal anti-inflammatory agents; anti-angiogenic factors; angiogenic factors and polymeric carriers containing such factors; anti-secretory factors; anticoagulants and/or antithrombotic agents; local anesthetics; ophthalmics; prostaglandins; anti-depressants; anti-psychotic substances; anti-emetics; imaging agents; biocidal/biostatic sugars such as dextran, glucose, etc.; amino acids; peptides; vitamins; inorganic elements; co-factors for protein synthesis; endocrine tissue or tissue fragments; synthesizers; enzymes such as alkaline phosphatase, collagenase, peptidases, oxidases, etc.; polymer cell scaffolds with parenchymal cells; collagen lattices; antigenic agents; cytoskeletal agents; cartilage fragments; living cells such as chondrocytes, bone marrow cells, mesenchymal stem cells; natural extracts; genetically engineered living cells or otherwise modified living cells; expanded or cultured cells; DNA delivered by plasmid, viral vectors, or other means; tissue transplants; autogenous tissues such as blood, serum, soft tissue, bone marrow, etc.; bioadhesives; bone morphogenic proteins (BMPs); osteoinductive factor (IFO); fibronectin (FN); endothelial cell growth factor (ECGF); vascular endothelial growth factor (VEGF); cementum attachment extracts (CAE); ketanserin; human growth hormone (HGH); animal growth hormones; epidermal growth factor (EGF); interleukins, for example, interleukin-1 (IL-1), interleukin-2 (IL-2); human alpha thrombin; transforming growth factor (TGF-beta); insulin-like growth factors (IGF-1, IGF-2); parathyroid hormone (PTH); platelet derived growth factors (PDGF); fibroblast growth factors (FGF, BFGF, etc.); periodontal ligament chemotactic factor (PDLGF); enamel matrix proteins; growth and differentiation factors (GDF); hedgehog family of proteins; protein receptor molecules; small peptides derived from growth factors above; bone promoters; cytokines; somatotropin; bone digesters; antitumor agents; cellular attractants and attachment agents; immuno-suppressants; permeation enhancers, for example, fatty acid esters such as laureate, myristate and stearate monoesters of polyethylene glycol, enamine derivatives, alpha-keto aldehydes, etc.; and nucleic acids.

In certain embodiments, the bioactive agent may be a drug. In some embodiments, the bioactive agent may be a growth factor, cytokine, extracellular matrix molecule, or a fragment or derivative thereof, for example, a protein or peptide sequence such as RGD.

In one embodiment of a covering comprising two compartments, a first growth factor may be provided for delivery by the first compartment and a second growth factor may be provided for delivery by the second compartment. The first and second growth factors may be provided with other substances. The first and second growth factors may be selected (and placed in respective compartment for positioning in vivo) based on desired characteristics of the growth factor. For example, an angiogenic growth factor may be provided in the first compartment and an osteoinductive growth factor may be provided in the second compartment.

Similarly, the substance delivered by the first compartment and the substance delivered by the second compartment may be selected based on desired characteristics of the compartment according to its placement in vivo. Thus, for example, one compartment may have a substance that is substantially osteoclast stimulating while another compartment may have a substance that is substantially osteoblast stimulating.

In one embodiment, demineralized bone fibers may be provided in the first compartment and surface demineralized bone chips may be provided in the second compartment. In this embodiment, the demineralized bone fibers may generally provide osteoinductive characteristics and the surface demineralized chips may generally provide osteoinductive and/or osteoconductive characteristics. In use, the covering may be laid flat on the transverse process and positioned such that the first compartment, holding the demineralized bone fibers, is nearest the vertebral body and the second compartment, holding the surface demineralized bone chips, is farther from the vertebral body, or the compartments may be positioned in any other desired configuration. In another embodiment, a covering may comprise first and second compartments wherein autograft may be placed in one of the compartments prior to placement of the covering in vivo, described more fully below. In other embodiments, three or more compartments may be used, as appropriate for the materials being delivered and the application of the compartmented implant. More than one substance may be provided in a compartment. For example, surface demineralized bone chips and demineralized bone fibers may be mixed and provided within a single compartment. Such mixture of substances within a single compartment may be a substantially uniform mix or may be a plurality of substances placed in the compartment separately such that they are substantially unmixed. When multiple compartments are used, each compartment may contain one or more substances. Exemplary substances that may be provided in one or more compartments of the delivery system include cells from the osteogenic precursors, growth factors, angiogenic factors and other active proteins including bone morphogenic proteins, and cellular scaffolding materials of natural or synthetic origin, antibiotics, and other substances described below.

In some embodiments, other medical devices may be provided within the covering. For example, one or more electrical stimulator electrodes may be provided within the covering.

Sterilization

The medical device and/or covering may be sterilizable. In various embodiments, one or more components of the medical device and/or covering are sterilized by radiation in a terminal sterilization step in the final packaging. Terminal sterilization of a product provides greater assurance of sterility than from processes such as an aseptic process, which require individual product components to be sterilized separately and the final package assembled in a sterile environment.

In various embodiments, gamma radiation is used in the terminal sterilization step, which involves utilizing ionizing energy from gamma rays that penetrates deeply in the device and/or covering. Gamma rays are highly effective in killing microorganisms, they leave no residues nor have sufficient energy to impart radioactivity to the device. Gamma rays can be employed when the device is in the package and gamma sterilization does not require high pressures or vacuum conditions, thus, package seals and other components are not stressed. In addition, gamma radiation eliminates the need for permeable packaging materials.

In various embodiments, electron beam (e-beam) radiation may be used to sterilize one or more components of the device and/or covering. E-beam radiation comprises a form of ionizing energy, which is generally characterized by low penetration and high-dose rates. E-beam irradiation is similar to gamma processing in that it alters various chemical and molecular bonds on contact, including the reproductive cells of microorganisms. Beams produced for e-beam sterilization are concentrated, highly-charged streams of electrons generated by the acceleration and conversion of electricity. E-beam sterilization may be used, for example, when the medical device and/or covering is included in a gel.

Other methods may also be used to sterilize the device and/or covering and/or one or more components of the device and/or covering, including, but not limited to, gas sterilization, such as, for example, with ethylene oxide or steam sterilization.

Methods of Use

The covering delivers the substance or substances in vivo. Such delivery may be active, passive, by diffusion, or other. Active delivery may include the degradation or decomposition of the covering with the interaction of body fluids, extracellular matrix molecules, enzymes or cells. It may also include the cleavage of physical and/or chemical interactions of substance from covering with the presence of body fluids, extracellular matrix molecules, enzymes or cells. Further, it may comprise formation change of substances (growth factors, proteins, polypeptides) by body fluids, extracellular matrix molecules, enzymes or cells.

The covering is loaded with the substance for placement in vivo. The covering may be pre-loaded, thus loaded at manufacture, or may be loaded in the operating room or at the surgical site. Preloading may be done with any of the substances previously discussed including, for example, DBM, synthetic calcium phosphates, synthetic calcium sulfates, enhanced DBM, collagen, carrier for stem cells, and expanded cells (stem cells or transgenic cells). Any other suitable method may be used for loading a substance in the covering in the operating room or at the surgical site. For example, the substance may be spooned into the covering, the substance may be placed in the covering using forceps, the substance may be loaded into the covering using a syringe (with or without a needle), or the substance may be inserted into the covering in any other suitable manner. Specific embodiments for loading at the surgical site include for vertebroplasty or for interbody space filler.

In various embodiments, loading in the operating room or at the surgical site can be done with any of these materials and further with autograft and/or bone marrow aspirate by adding the desired material through the filling means or funnel 400 by gravity using a spoon and/or a plunger to push the material through. For example, the surgeon can grasp the covering or bag 102 depicted in FIG. 1 and proceed to load compartment 108 with autograft via funnel 400 through opening 120 of covering 102. Thereafter, once compartment 108 is full, funnel 400 is removed and drawstrings 116 and 118 can also be removed by pulling them off from the device. Once drawstrings 116 and 118 are removed, bag flap 122 is sealed closed and DBM and autograft particles can be thoroughly mixed in covering or bag 102 thereby optimizing the biological environment for inducing new bone growth at the selected surgical site.

For placement, the substance or substances may be provided in the covering and the covering placed in vivo. In one embodiment, the covering is placed in vivo by placing the covering in a catheter or tubular inserter and delivering the covering with the catheter or tubular inserter. The covering, with a substance provided therein, may be steerable such that it can be used with flexible introducer instruments for, for example, minimally invasive spinal procedures. For example, the osteoimplant may be introduced down a tubular retractor or scope, during XLIF, TLIF, or other procedures. In other embodiments, the covering (with or without substance loaded) may be placed in a cage, for example for interbody fusion.

In continuous tube embodiments, the surgeon may divide the tube into the desired number of compartments, using a crimper, heat tool or other. Alternatively, in an embodiment wherein the tube is perforated into a plurality of compartments, the surgeon may select the number of compartments desired and cut along the applicable perforation. In some embodiments, some of the compartments may be prefilled with a substance for delivery and other compartments may be empty for filling by the surgeon. For example, ever other compartment between perforations may be preloaded or filled. The osteoimplant thus may be customized by filling the empty compartments with a desired substance.

Attachment mechanisms provided on the covering may be used to couple the covering to a site in vivo.

The covering may be used in any suitable application. In some embodiments, the covering may be used in healing vertebral compression fractures, interbody fusion, minimally invasive procedures, posterolateral fusion, correction of adult or pediatric scoliosis, treating long bone defects, osteochondral defects, ridge augmentation (dental/craniomaxillofacial, e.g. edentulous patients), beneath trauma plates, tibial plateau defects, filling bone cysts, wound healing, around trauma, contouring (cosmetic/plastic/reconstructive surgery), and others. The delivery system may be used in a minimally invasive procedure via placement through a small incision, via delivery through a tube, or other. The size and shape may be designed with restrictions on delivery conditions. In some embodiments, pieces of the covering can be separated by pulling or tearing force applied along separation assists if present in a multi compartment configuration and the pieces of the covering can be used to surround the bone defect. For examples, 3 pieces of the torn covering can be placed around the bone defect to triangulate bone growth by the influx of cells, in, at or near the bone defect.

In some embodiments, the covering is flexible enough so that the covering can be folded upon itself before it is implanted at, near or in the bone defect.

An exemplary application for using a delivery system as disclosed is fusion of the spine. In clinical use, the covering and delivered substance may be used to bridge the gap between the transverse processes of adjacent or sequential vertebral bodies. The delivery system may be used to bridge two or more spinal motion segments. The covering surrounds the substance to be implanted, and contains the substance to provide a focus for healing activity in the body.

In other applications, the delivery system may be applied to transverse processes or spinous processes of vertebrae.

Generally, the delivery system may be applied to a pre-existing defect, to a created channel, or to a modified defect. Thus, for example, a channel may be formed in a bone, or a pre-existing defect may be cut to form a channel, for receipt of the delivery system. The covering may be configured to match the channel or defect. In some embodiments, the configuration of the covering may be chosen to match the channel. In other embodiments, the channel may be created, or the defect expanded or altered, to reflect a configuration of the covering. The covering may be placed in the defect or channel and, optionally, coupled using attachment mechanisms.

At the time just prior to when the delivery system is to be placed in a defect site, optional materials, for example, autograft bone marrow aspirate, autograft bone, preparations of selected autograft cells, autograft cells containing genes encoding bone promoting action, can be combined with the covering and/or with a substance provided within the covering prior to or during the surgical procedure. The osteoimplant can be implanted at the bone repair site, if desired, using any suitable affixation means, for example, sutures, staples, bioadhesives, screws, pins, rivets, other fasteners and the like or it may be retained in place by the closing of the soft tissues around it.

It will be apparent to those skilled in the art that various modifications and variations can be made to various embodiments described herein without departing from the spirit or scope of the teachings herein. Thus, it is intended that various embodiments cover other modifications and variations of various embodiments within the scope of the present teachings. 

What is claimed is:
 1. A delivery system comprising a porous polymer mesh covering comprising a body having at least two compartments, the at least two compartments comprising a first compartment and a second compartment, the first compartment containing a first therapeutic agent and the second compartment configured to receive a second therapeutic agent, wherein the porous polymer mesh covering retains the first therapeutic agent for mixing with the second therapeutic agent prior to delivery at a surgical site, and the delivery system comprises a funnel having an opening configured to receive the second therapeutic agent and to fit in the porous polymer mesh covering to fill the second compartment with the second therapeutic agent, the funnel having an attachment member to removably attach the funnel to the porous polymer mesh covering for filling the second compartment, and the porous polymer mesh covering further comprises edges comprising polymers that are different and more hydrophilic than polymers that comprise the body.
 2. A delivery system according to claim 1, wherein the second compartment is unfilled.
 3. A delivery system according to claim 1, wherein the first compartment and the second compartment are separated by at least one removable separation member.
 4. A delivery system according to claim 3, wherein the at least one removable separation member comprises a pull string or drawstring.
 5. A method of treating a bone defect in a patient in need of such treatment, the method comprising implanting into the bone defect a delivery system according to claim
 3. 6. A method of treating a bone defect according to claim 5, further comprising mixing of the first and second therapeutic agents by removing the removable separation member.
 7. A method of treating a bone defect according to claim 5, further comprising shrinking the delivery system by removing the removable separation member.
 8. A method of treating a bone defect according to claim 5, further comprising attaching the funnel to the second compartment.
 9. A method for treating a bone defect according to claim 5, further comprising filling the second compartment with the second therapeutic agent.
 10. A method for treating a bone defect according to claim 5, wherein the first therapeutic agent comprises demineralized bone matrix and the second therapeutic agent comprises protein, carbohydrate, lipid, collagen, allograft bone, autograft bone, tricalcium phosphate, hydroxyapatite, a growth and differentiation factor, a carrier for a growth factor, a growth factor extract of tissue, bone marrow aspirate, concentrates of lipid derived or marrow derived adult stem cells, umbilical cord derived stem cells, committed or partially committed cells from osteogenic or chondrogenic lineage, an antimicrobial, an antibiotic, a statin, or combinations thereof.
 11. A delivery system according to claim 1, wherein the attachment member is configured to attach to the second compartment to allow the funnel to fill the second compartment with the second therapeutic agent.
 12. A delivery system according to claim 11, wherein the attachment member comprises a spring loaded clip.
 13. A delivery system according to claim 1, wherein the first therapeutic agent comprises demineralized bone matrix and the second therapeutic agent comprises protein, carbohydrate, lipid, collagen, allograft bone, autograft bone, tricalcium phosphate, hydroxyapatite, a growth and differentiation factor, a carrier for a growth factor, a growth factor extract of tissue, bone marrow aspirate, concentrates of lipid derived or marrow derived adult stem cells, umbilical cord derived stem cells, committed or partially committed cells from osteogenic or chondrogenic lineage, an antimicrobial, an antibiotic, a statin, or combinations thereof.
 14. A delivery system comprising a porous polymer mesh covering configured for implantation into a bone defect site, the porous polymer mesh covering comprising a body having at least two compartments, the at least two compartments comprising a first compartment and a second compartment, the first compartment containing a first therapeutic agent and the second compartment is unfilled and configured to receive a second therapeutic agent, wherein the porous polymer mesh covering retains the first therapeutic agent for mixing with the second therapeutic agent prior to delivery at a surgical site, the at least two compartments being separated by at least one removable separation member, the second compartment defining an opening, and the delivery system comprises a filling member having an opening and a mating surface configured to mate with a mating surface of the porous polymer mesh covering to fill the second compartment with the second therapeutic agent, the filling member having an attachment member to removably attach the filling member to the porous polymer mesh covering for filling the second compartment, and the porous polymer mesh covering further comprises edges comprising polymers that are different and more hydrophilic than polymers that comprise the body.
 15. A delivery system according to claim 14, wherein the at least one removable separation member comprises a pull string.
 16. A delivery system according to claim 14, wherein the attachment member comprises a spring loaded clip and the filling member comprises a funnel. 